Strain-shielding induced by press-fit and cemented femoral stems in revision TKA

Abstract

Revision Total Knee Arthroplasty is becoming an increasingly common reconstructive procedure. Bone loss is commonly encountered at the time of revision. Restoration of lost bone support and joint stability are the primary challenges in revision TKA. Contemporary knee systems often include revision components with use of modular stems to achieve support and stability. The aim of this study was to evaluate the strainshielding effect in cancellous and cortical bone next to the femoral component with use of cemented and press-fit stems. The difficulties to evaluate these biomechanical parameters invitro makes the use of finite element (FE) models a way to evaluate them. The FE results demonstrate strain-shielding induced by both types of stems along their length and can provoke bone repsortion. Under the femoral component the cemented stem presented the highest strain-shielding effect, especially in the region next to the stem fixation. Contrasting to the press-fit stem, the increase of strains in the lateral and medial limits of the femoral component was smaller for the cemented stem, and can reduce the risk of in vivo bone fatigue damage. Pain around the femoral stem tip region after revision TKA referred in several clinical studies may be correlated with high bone strains originated by the extremity of the press-fit stem.